<template>
  <div>
    <div class="goods">
      <div class="menu-wrapper" ref="left">
        <ul ref="leftUl">
          <!-- index 是所有的下标【包含当前的下标】， currentIndex是当前的下标 -->
          <li
            class="menu-item"
            :class="{current: index===currentIndex}"
            v-for="(item, index) in goods"
            :key="index"
            @click="goToMenu(index)"
          >
            <span class="text bottom-border-1px">
              <img class="icon" :src="item.icon" v-if="item.icon" />
              {{item.name}}
            </span>
          </li>
        </ul>
      </div>
      <div class="foods-wrapper" ref="right">
        <ul ref="rightUl">
          <li class="food-list-hook" v-for="(item,index) in goods" :key="index">
            <h1 class="title">{{item.name}}</h1>
            <ul>
              <li
                class="food-item bottom-border-1px"
                v-for="(food,index) in item.foods"
                :key="index"
                @click="showFood(food)"
              >
                <div class="icon">
                  <img width="57" height="57" :src="food.icon" />
                </div>
                <div class="content">
                  <h2 class="name">{{food.name}}</h2>
                  <p class="desc ellipsis">{{food.description}}</p>
                  <div class="extra">
                    <span class="count">月售{{food.sellCount}}份</span>
                    <span>好评率{{food.rating}}%</span>
                  </div>
                  <div class="price">
                    <span class="now">￥{{food.price}}</span>
                    <span class="old" v-if="food.oldPrice">￥{{food.oldPrice}}</span>
                  </div>
                  <div class="cartcontrol-wrapper">
                    <cart-control :food="food" />
                  </div>
                </div>
              </li>
            </ul>
          </li>
        </ul>
      </div>
    </div>
    <!-- 购物车 -->
    <ShopCart></ShopCart>

    <!-- 弹框大图 -->
    <PreviewFood ref="prevfood" :food="food"></PreviewFood>
  </div>
</template>

<script>
import {mapState} from 'vuex'
import BScroll from 'better-scroll'
import ShopCart from '../../../components/content/shopcart/ShopCart'
import PreviewFood from '../../../components/content/previewfood/PreviewFood'
export default {
  data () {
    return {
       scrollY: 0,
       lisHeight: [],
      //  需要传给子组件的food
       food: {}
    };
  },
  computed:{
    ...mapState({
      goods: state => state.shop.shop_goods
    }),

    // 当前的索引下标
    currentIndex(){
      // 根据右侧列表来判断
      const {lisHeight, scrollY} = this
      // 获取到当前处于哪一个位置
      const index = lisHeight.findIndex((liHeight,index) => scrollY >= liHeight && scrollY < lisHeight[index+1])
      // 计算新的下标来确认是否需要往上或往下滑动
      if(index !== this.index && this.leftScroll){
        this.index = index
        // 让左侧列表滑动到对应的li
        const li = this.$refs.leftUl.children[index]
        this.leftScroll.scrollToElement(li,100)
      }

      return index
    }
  },
  mounted() {
    this._initScroll()
    this._initTops()
  },
  watch: {
    goods(){
        this.$nextTick(() => {
          this._initScroll()
          this._initTops()
        })
    }
  },
  methods: {
    _initScroll(){
      if(!this.leftScroll){
          this.leftScroll = new BScroll(this.$refs.left, {
          click: true,
          probeType: 1,
        })
      }

      if(!this.rightScroll){
        this.rightScroll = new BScroll(this.$refs.right, {
          click: true,
          probeType: 1,
        })
      }

      // 通过监听scroll的滚动来获取当前应该选中哪一个分类
      this.rightScroll.on('scroll',({x,y}) => {
        console.log(x,y)
        this.scrollY = Math.abs(y)
      })

      // 解决惯性滑动时左侧分类class不改变的情况
      this.rightScroll.on('scrollEnd',({x,y}) => {
        this.scrollY = Math.abs(y)
      })
    },

    // 获取右侧所有分类li的高度
    _initTops(){
      const tops = []
      let top = 0
      tops.push(top)
      const lis = this.$refs.rightUl.children
      Array.prototype.forEach.call(lis, (li) => {
        top += li.clientHeight
        tops.push(top)
      })
      this.lisHeight = tops
    },

    // 点击左侧列表，右侧内容快速定位到具体的地方
    goToMenu(index){
      const top = this.lisHeight[index]
      // 立即更新左侧选中项
      this.scrollY = top

      // 到达指定的位置（由于存放的值为正，但是向下滑需要负值，这里就设置为负值）
      this.rightScroll.scrollTo(0,-top,500)
    },

    showFood(food){
      // 需要传给子组件的food
      this.food = food
      this.$refs.prevfood.toggleShow()
    }
  },
  components:{
    ShopCart,
    PreviewFood
  }
}
</script>

<style lang='less' scoped>
.goods {
  display: flex;
  position: absolute;
  top: 225px;
  bottom: 46px;
  width: 100%;
  background: #fff;
  overflow: hidden;
  .menu-wrapper {
    flex: 0 0 80px;
    width: 80px;
    background: #f3f5f7;
    .menu-item {
      display: table;
      height: 54px;
      width: 56px;
      padding: 0 12px;
      line-height: 14px;
      &.current {
        position: relative;
        z-index: 10;
        margin-top: -1px;
        background: #fff;
        color: #02a774;
        font-weight: 700;
      }

      .icon {
        display: inline-block;
        vertical-align: top;
        width: 12px;
        height: 12px;
        margin-right: 2px;
        background-size: 12px 12px;
        background-repeat: no-repeat;
      }

      .text {
        display: table-cell;
        width: 56px;
        vertical-align: middle;
        font-size: 12px;
      }
    }
  }

  .foods-wrapper {
    flex: 1;
    .title {
      padding-left: 14px;
      height: 26px;
      line-height: 26px;
      border-left: 2px solid #d9dde1;
      font-size: 12px;
      color: rgb(147, 153, 159);
      background: #f3f5f7;
    }

    .food-item {
      display: flex;
      margin: 18px;
      padding-bottom: 18px;
      position: relative;
      &:last-child {
        margin-bottom: 0;
      }
      .icon {
        flex: 0 0 57px;
        margin-right: 10px;
      }

      .content {
        flex: 1;
        .name {
          margin: 2px 0 8px 0;
          height: 14px;
          line-height: 14px;
          font-size: 14px;
          color: rgb(7, 17, 27);
        }
        .desc,
        .extra {
          line-height: 10px;
          font-size: 10px;
          color: rgb(147, 153, 159);
        }
        .desc {
          line-height: 12px;
          margin-bottom: 8px;
        }
        .extra {
          .count {
            margin-right: 12px;
          }
        }
        .price {
          font-weight: 700;
          line-height: 24px;
          .now {
            margin-right: 8px;
            font-size: 14px;
            color: rgb(240, 20, 20);
          }

          .old {
            text-decoration: line-through;
            font-size: 10px;
            color: rgb(147, 153, 159);
          }
        }

        .cartcontrol-wrapper {
          position: absolute;
          right: 0;
          bottom: 12px;
        }
      }
    }
  }
}
</style>